haemoglobin

Question 1

Describe how haemoglobin normally loads oxygen in the lungs and unloads it in a tissue cell.

Answer 1

. Oxygen combines (reversibly) to produce oxyhaemoglobin;
. each haemoglobin molecule/ one haemoglobin may transport 4 molecules of oxygen;
. high partial pressure of oxygen / oxygen tension / concentration in lungs;
. haemoglobin (almost) 95% / 100% saturated;
. unloads at low oxygen tension(in tissues);
. presence of carbon dioxide displaces curve further to right / increases oxygen dissociation;
. allows more O2 to be unloaded;
. increase temp/ acidity allows more O2 to be unloaded;
. low pO2 / increase CO2 / increase term / increase acid occur in vicinity of respiring tissue;

Question 2

Explain how oxygen in a red blood cell is made available for respiration in active tissues.

Answer 2

. CO2 (increased) respiration;
. (increased) dissociation oxygen from haemoglobin;
. Low partial pressure in tissues/plasma;
. Oxygen diffuses from red blood cell to tissues;

Question 3

The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus.

Answer 3

. Higher affinity / loads more oxygen;
. At low/same/high partial pressure/pO2;
. Oxygen moves from mother/to fetus;

Question 4

Explain how oxygen is loaded, transported and unloaded in the blood. (6)

Answer 4

. Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
. In red blood cells;
. Loading/uptake/association in lungs at high p.O2;
. Unloads/ dissociates / releases to respiring cells/tissues at low p.O2;
. Unloading linked to higher carbon dioxide (concentration);

Question 5

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why.

Answer 5

. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin; [conformational shift caused]
. Creates / leads to / uncovers second / another binding site OR Uncovers another iron / Fe / haem group to bind to;

Question 6

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin

Answer 6

. Increases/more oxygen dissociation/unloading OR Deceases haemoglobin’s affinity for O2;
. (By) decreasing (blood) pH/increasing acidity;

Question 7

Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobin (5)

Answer 7

. Smaller mammal has greater surface area to volume ratio;
. Smaller mammal/larger SA:Vol ratio more heat lost (per unit body mass);
. Smaller mammal/larger SA:Vol ratio has greater rate of respiration/metabolism;
. Oxygen required for respiration;
. (Haemoglobin) releases more oxygen / oxygen released more readily / haemoglobin has lower affinity;